This invention relates to an input device for a sewing machine capable of following stitch pattern control programs. More particularly, the invention relates to a sewing machine input device having scaling functions.
Recent times have witnessed the introduction of an electronically controlled sewing machine capable of memorizing stitch patterns as coordinate values which are inputted onto magnetic tape, magnetic card or floppy disc memories. On such sewing machines, a work holder is subsequently moved by a stepper motor receiving the programmed stitch pattern coordinate values.
Conventionally, as input equipment for the known electronically controlled sewing machine, a digitizer (graph drawing apparatus) with indicating pen is provided. To memorize coordinate values of a pattern, an indicating pen is used to portray the stitch pattern on the digitizer. Thus, a stitch pattern 2 as shown in FIG. 1 is formed using the aforementioned digitizer input device. Back tack portion 1 (FIG. 1) of the pattern is generally standardized; its length and number of stitches are fixed for each workpiece.
In certain situations it may be desirable to provide a scaling factor to an inputted stitch pattern such that the inputted stitch pattern coordinates will be scaled up or scaled down prior to recordation. This is to account for oversized stitch patterns. See the copending patent application "SEWING MACHINE INPUT DEVICE HAVING SCALING FUNCTION," referenced above.
However, scale up or scale-down of the back tack portion is generally not desirable. According to known input devices, however, it is impossible to input stitch patterns which include scale up prohibited or scale-down prohibited portions. Therefore, as FIG. 2 shows, when the pattern 2 is scaled up, the back tack portion is also scaled up. This is a weakness inherent in known scaling systems. To compensate for this weakness, it was, in the past, necessary to separately input the back tack portions of the stitch patterns.
It is therefore an object of the invention to provide an input device for an electronically controlled sewing machine which is effective for inputting stitching patterns which include portions for which scaling up or scaling down are not desired.
It is a further object of the invention to provide an input device which is effective for inputting scaling-prohibited portions without the need for separately inputting tacking portions.